1. Field of the Invention
This invention relates in general to steering systems, and in particular, to a compliant steering gear assembly.
2. Description of the Related Art
Steering systems in motor vehicles typically comprise rack and pinion steering systems. The rack and pinion steering systems consist of a pinion shaft, pinion teeth, a rack including rack teeth, and a housing. The housing houses a hydraulic valve section, an extended rack section, and houses the meshing of the pinion teeth and the rack teeth. The housing is commonly supported by one or more mounting brackets. The mounting brackets are secured to the housing and are bolted to a vehicle frame or a unibody structure. Rubber grommets or bushings disposed between the mounting bracket and the vehicle frame are typically used to dampen noise and vibrations from the road.
The mounting brackets typically are either rigid to prevent movement of the steering gear assembly relative to the vehicle frame or resilient to accommodate movement of the steering gear assembly relative to the vehicle frame. Typically when a vehicle is cornering at low lateral acceleration forces, it is desirable to have the steering gear assembly rigid so that the steerable gears are immediately responsive to the driver's demands. At increased lateral acceleration forces, lateral movement of the steering gear assembly (i.e., a resilient mounting of the steering gear relative to the vehicle frame) is desirable in order to create an understeer condition. That is, when lateral movement of the steering gear assembly occurs, the steering wheel must be rotated an additional number of degrees before the driver's intended steering affect is produced. The steering system will respond with a smaller steering angle than if the steering gear assembly were rigidly mounted to the vehicle. The understeer condition is more desirable as the vehicle approaches adhesion limits than an oversteer condition at the adhesion limits.
Thus, it is desirable to have a steering system which maintains a rigidly mounted steering gear assembly when low lateral acceleration forces are exerted on the vehicle and changes to a compliant steering gear assembly when high lateral acceleration forces are exerted on the vehicle.